ALARP

ALARP stands for "as low as reasonably practicable", and is a term often used in the regulation and management of safety-critical and safety-involved systems. The ALARP principle is that the residual risk shall be reduced as far as reasonably practicable. In UK and NZ Health and Safety law, it is equivalent to SFAIRP (So Far As Is Reasonably Practicable). ALARA (As Low As Reasonably Achievable) is a similar term used in USA.

For a risk to be ALARP, it must be possible to demonstrate that the cost involved in reducing the risk further would be grossly disproportionate to the benefit gained. The ALARP principle arises from the fact that infinite time, effort and money could be spent in the attempt of reducing a risk to zero. It should not be understood as simply a quantitative measure of benefit against detriment. It is more a best common practice of judgement of the balance of risk and societal benefit.

In this context, risk is the combination of the frequency (likelihood) and the consequence of a specified hazardous event.

The following factors are likely to be considered when deciding whether or not a risk has been reduced as far as reasonably practical.

Another factor that often comes into the ALARP principle, is the cost of assessing the improvement gained in an attempted risk reduction. In extremely complex systems, this can be very high, and could be the limiting factor in practicability of risk reduction, although according to HSE guidance, cost alone should never be a justification for taking extra safety risks.

Determining that a risk has been reduced to ALARP involves an assessment of the risk to be avoided, of the sacrifice (in money, time and trouble) involved in taking measures to avoid that risk, and a comparison of the two. This is a cost–benefit analysis.

The term ALARP arises from UK legislation, particularly the Health and Safety at Work etc. Act 1974, which requires "Provision and maintenance of plant and systems of work that are, so far as is reasonably practicable, safe and without risks to health". The phrase So Far As is Reasonably Practicable (SFARP) in this and similar clauses is interpreted as leading to a requirement that risks must be reduced to a level that is As Low As is Reasonably Practicable(ALARP).

The key question in determining whether a risk is ALARP is the definition of reasonably practicable. This term has been enshrined in the UK case law since the case of Edwards v. National Coal Board in 1949. The ruling was that the risk must be significant in relation to the sacrifice (in terms of money, time or trouble) required to avert it: risks must be averted unless there is a gross disproportion between the costs and benefits of doing so.

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